DescTools (version 0.99.19)

SetAlpha: Add an Alpha Channel To a Color

Description

Add transparency to a color defined by its name or number. The function first converts the color to RGB and then appends the alpha channel.

Usage

SetAlpha(col, alpha = 0.5)

Arguments

col

vector of two kind of R colors, i.e., either a color name (an element of colors()) or an integer i meaning palette()[i].

alpha

the alpha value to be added. This can be any value from 0 (fully transparent) to 1 (opaque). NA is interpreted so as to delete a potential alpha channel. Default is 0.5.

Value

Vector with the same length as col, giving the rgb-values extended by the alpha channel as hex-number (#rrggbbaa).

Details

All arguments are recyled as necessary.

See Also

ColToHex, col2rgb

Examples

SetAlpha("yellow", 0.2)
SetAlpha(2, 0.5)   # red

Canvas(3)
DrawCircle(x=c(-1,0,1), y=c(1,-1,1), r.out=2, col=SetAlpha(2:4, 0.4))

x <- rnorm(15000)
par(mfrow=c(1,2))
plot(x, type="p", col="blue" )
plot(x, type="p", col=SetAlpha("blue", .2), main="Better insight with alpha channel" )